Abstract The threshing unit of a combine comprises a multiphase flow; therefore, it is essential to consider it on the basis of the flow model. In this study, flight simulation by DEM with fixed wind velocity was carried out. The grain and straw were considered to be ellipsoidal and cuboidal, respectively. A two-dimensional model coupling with a circle element was constructed. Each flight trajectory was reproduced in terms of the initial conditions and changes in winnowing velocity. The average flight velocity of the grain was 0.2 m/s higher than that measured in the experiment. It can simulate to closer phenomenon by mixing different particle mass and straw, analyzing the increase in particles and linking it with fluid analysis.